This invention relates to a fluid pressure modulator for use, for example, in a current to pressure transducer system.
Current to pressure transducer systems have been used for some time to control output fluid pressure in a fluid carrying line. This control is effected by controlling bleed-off of the fluid in some type of pressure modulating device. The pressure modulating device, which is controlled by an electrical input signal, is connected to the fluid-carrying line to increase the bleed-off if less output pressure is desired and to decrease the bleed-off if a greater output pressure is desired. A pressure sensor senses the fluid output pressure and supplies an electrical signal representing that pressure to a comparator. The electrical input signal, whose value is to determine the output fluid pressure, is also supplied to the comparator and compared to the signal representing the sensed output pressure. If there is a difference between the two compared signals, the comparator supplies an electrical adjustment signal to the pressure modulator to either increase or decrease the bleed-off so that as to bring the output fluid pressure closer to the desired output pressure as represented by the value of the electrical input signal. In this manner, the fluid output pressure can be controlled and varied by varying the value of the electrical input signal. The above current to pressure transducer system is fairly conventional and systems similar to this, or at least component parts useable in such systems, are disclosed in U.S. Pat. Nos. 4,534,376, 4,481,967, 4,492,246, 4,325,399, 4,653,523, and 4,636,830.
Although there exist a variety of systems for controlling the output fluid pressure in a fluid carrying line by controlling bleed-off of the fluid, such systems oftentimes lack accuracy and precision, are sensitive to vibration, are sensitive to the mounting of the pressure modulating device, either do not allow for calibration or calibration is complicated, and generally are complicated in design and operation.